Retrofit Double Glazing NZ: Complete 2025 Guide
Retrofit double glazing (also called secondary glazing) adds a second pane of glass to your existing windows without replacing the frames. It costs $200-$400 per window in New Zealand - around 50% cheaper than full window replacement - and delivers 70-80% of the insulation benefits.
Retrofit Double Glazing Prices NZ (2025)
Retrofit double glazing is the most affordable way to upgrade your windows. Here's what you'll pay in 2025:
| Window Size | Retrofit Cost | Full Replacement Cost | Savings |
|---|---|---|---|
| Small (0.5m²) | $200 - $280 | $500 - $700 | ~60% |
| Medium (1m²) | $280 - $350 | $800 - $1,000 | ~65% |
| Large (1.5m²) | $350 - $450 | $1,200 - $1,600 | ~70% |
| Whole Home (10-15 windows) | $2,500 - $5,000 | $8,000 - $20,000 | ~70% |
Retrofit vs Full Replacement: Which is Right for You?
Choose Retrofit If:
- ✓ Your existing frames are in good condition
- ✓ You have a limited budget ($2,500-$5,000)
- ✓ You want to preserve character windows
- ✓ You need minimal disruption (1-2 days)
- ✓ You're renting and need landlord approval
Choose Full Replacement If:
- ✓ Your frames are rotting, warped, or damaged
- ✓ You want maximum insulation (Low-E, argon)
- ✓ You're doing a major renovation
- ✓ You want a 25+ year solution
- ✓ You need different window sizes or styles
How Retrofit Double Glazing Works
The retrofit installation process is straightforward and minimally disruptive:
Assessment & Measurement
A technician inspects your existing windows and takes precise measurements. They'll check frame condition and advise if retrofit is suitable.
Custom Manufacturing
Double-glazed units are custom-made to fit your exact window dimensions. This typically takes 2-3 weeks.
Remove Existing Glass
The single-pane glass is carefully removed from your existing frame. The frame is cleaned and prepared.
Install Double-Glazed Unit
The new sealed double-glazed unit is fitted into your existing frame with weather-tight seals.
Seal & Finish
Final sealing, glazing beads installed, and cleanup. Each window takes 1-2 hours.
Benefits of Retrofit Double Glazing
Thermal Performance
- • 30-40% reduction in heat loss
- • Warmer rooms in winter
- • Cooler rooms in summer
- • Reduced condensation on windows
Noise Reduction
- • 50-60% noise reduction
- • Blocks traffic and street noise
- • Quieter home environment
- • Better sleep quality
Cost Savings
- • $300-$600/year energy savings
- • ROI in 4-7 years
- • Increases property value
- • No building consent costs
Practical Benefits
- • Preserves character windows
- • Quick 1-2 day installation
- • No structural changes needed
- • 10-15 year warranty typical
Get Free Retrofit Double Glazing Quotes
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Get Free QuotesFrequently Asked Questions
Is retrofit double glazing as good as replacement windows?
Retrofit delivers 70-80% of the thermal performance of full replacement at 50% of the cost. For most NZ homes with sound frames, it's the smart choice. Full replacement only makes sense if frames are damaged or you want premium features like Low-E glass and argon fill.
How much does retrofit double glazing cost in NZ?
Retrofit double glazing costs $200-$400 per window depending on size. A typical 3-bedroom home with 10-15 windows costs $2,500-$5,000 total. This is 50-70% cheaper than full window replacement ($8,000-$20,000).
Can I retrofit double glazing myself (DIY)?
DIY retrofit is possible but not recommended. Professional installation ensures proper sealing, warranty coverage, and correct measurements. Poor installation leads to condensation between panes, drafts, and failed seals. Most NZ retrofit companies include installation in their quotes.
Do I need building consent for retrofit double glazing?
No. Retrofit double glazing doesn't require building consent in New Zealand because you're not changing the window size, structure, or external appearance. This saves $1,000-$2,000 compared to new window installations that may need consent.
How long does retrofit double glazing last?
Quality retrofit double glazing lasts 15-20 years. Most NZ installers offer 10-year warranties on sealed units. The lifespan depends on seal quality, installation workmanship, and frame condition.
What types of windows can be retrofitted?
Most timber and aluminium windows can be retrofitted, including casement, awning, sliding, and fixed windows. Steel windows and very old timber frames may not be suitable. A professional assessment will confirm if your windows qualify.
Find Retrofit Installers in Your Area
Retrofit double glazing is available throughout New Zealand. Find installers in your region: